This project is a biological correlative study with three major objectives: 1. To carry out a systematic analysis of the expressio of thioredoxin in primary childhood T- and B- lineage acute lymphoblastic leukemia (ALL). 2. To correlate overexpression of thioredoxin with clinical features and outcome and determine if thioredoxin expression is higher at relapse as compared to samples at diagnosis 3. To examine the possible exploitation of the altered expression for future development of therapeutic interventions.